Numerous photopolymerizable coating compositions are known which may be used to make photo-imaging materials that are insensitive to light in the visible region of the spectrum and which may, therefore, be handled under conditions of ambient daylight or fluorescent illumination. Although preferred in copying processes, other materials which are sensitive to visible radiation must be protected from ambient illumination in order to prevent premature, indiscriminate polymerization in the photosensitive composition. Dye sensitized photopolymerizable layers such as disclosed in U.S. Pat. Nos. 2,875,047 and 3,573,922 may be handled under ambient illumination; however, such manipulation without safelight conditions must necessarily be limited to very short periods in order to ensure against formation of non-image polymerization, or "fog".
Common to most photo-imaging systems is the requirement that the photosensitive material be capable of inactivation subsequent to imagewise light exposure in order to "fix" the resulting image. Several methods of fixing have been previously employed, such as washing to remove active ingredients or deactivating such components with heat or chemical agents. The usual result of these procedures is that the imaging materials are limited to "one-shot" utility, since they are photosensitive until a first imaging exposure and are thereafter "fixed" against any further imaging capability.